This invention relates to a Transmit/Receive Module for Active Phased Array Antennas and more specifically to a Transmit/Receive module for L-Band Active Phased Array Antennas/Apertures which are employed in long range Active Phased Array Radars.
A Radar based on Active Phased Array Antenna System basically includes a plurality of active radiating antenna elements each of which is driven by/drives an individual Transmit/Receive module located closely adjacent thereto. Active Phased Arrays or Active Aperture Arrays, are being utilised in modern day Radar Systems. The active Array architecture overcomes the major Passive Array problems viz, low reliability inherent with tube type Radar Transmitters and their attendant high voltage power supplies and modulation, and the losses presented by their reciprocal ferrite/PIN diode phase shifters with the associated Passive Array RF manifold. Active Phased Arrays use individual solid-state T/R microwave module element at each of its radiating element (antenna), thus avoiding the distribution and phase shifter losses encountered in the Passive Array design. For the same radiated power, Active Phased Array Systems have been found to be significantly efficient, smaller and lighter than the conventional Passive Array systems. Need to generate very large power to obtain large power aperture product for long-range surveillance can be satisfied only with Active Phased Array Systems utilising Active Aperture Array techniques.
The performance of modern radar systems with Active Phased Array Antennas is mainly driven by the performance of the Transmit/Receive modules utilised in the system. As mentioned above, A Radar System with Active Phased Array Antenna may utilise a large number of Transmit/Receive modules, each connected to individual radiating elements (antenna) of the Active Array. In fact, the key element of the Active Phase Phased Array is the Transmit/Receive microwave module whose performance decides the overall performance of the Radar. A long range Radar working in L-band (1.2-1.4 GHz) may typically employ 200 individual Transmit/Receive modules. The performance of Radar system with Active Phase Phased Array Antenna is critically dependent on the availability of compact and minimum weight, low consumption and high reliability microwave Transmit/Receive modules. The major functions of a Transmit/Receive module are the generation of the transmit power, the low noise amplification of the received signals coupled to and received from the respective radiating element, the phase shift in the transmit and receive mode for beam steering, and the variable gain setting for aperture weighting during reception. The Transmit/Receive module architecture is closely related to the functionality required in the Active Apertures of the Array in which it is used.
Parameters that determine T/R module architecture are: (1) the need for a high transmit power with maximized power added efficiency, (2) the need to maximize receive input 3rd order intercept with a low front-end noise figure, (3) the need for self-calibration and built-in test capability in the module, (4) the need for low array sidelobes on receive mode, (5) the need for a distributed beam steering computation, and (6) the need for an effective heat transfer with a low module weight and cost.
The Transmit/receive modules utilised in Active Phased array Antennas are known in the art. However, these Transmit/Receive modules, known in the art suffer from following disadvantages.
Primary disadvantage of Transmit/Receive modules, known in the art, is that these are realized through Microwave Integrated Circuit (MIC) architecture thereby making the size of the T/R module bulky.
Another disadvantage of Transmit/Receive modules, known in the art, is that reliability of these T/R modules is less because of large number of interconnects therein.
Yet another disadvantage of Transmit/Receive modules, known in the art, is that their repeatability characteristics for phase and amplitude over all the Transmit/Receive Modules is very low.
Still further disadvantage of Transmit/Receive modules, known in the art, is that their phase and amplitude setting accuracy is inferior.
Yet another disadvantage of Transmit/Receive modules, known in the art, is that these are not cost effective.
Primary object of the present invention is to provide a Transmit/Receive (T/R) module which is realized through hybrid architecture of Microwave Integrated Circuit (MIC) and Monolithic Microwave Integrated Circuit (MMIC) both thereby helping In miniaturizing the complete T/R module.
Another object of the present invention is to provide a Transmit/Receive module in which the transmit chain is realised through MIC architecture thus enabling it to handle high level of output power necessary for long range radars.
Yet another object of the present invention is to provide a Transmit/Receive module in which the receive chain is realised through MMIC architecture thus helping in miniaturizing the receiver module.
Yet further object of the present invention is to provide a Transmit/Receive Module in which the transmit chain can provide high peak and average power output thereby enhancing the range capability of the Radar.
Still another object of the present invention is to provide a Transmit/Receive module in which high cooling efficiency is realised utilising cold plate with embedded microchannels underneath each of the power devices in Transmit Module.
Still further object of the present invention is to provide a Transmit/Receive module, which is capable of operating in entire L-band Radar frequency.
Still another object of the present invention is to provide a Transmit/Receive module, which has a low noise figure and a linear gain.
Yet another object of the present invention is to provide a Transmit/Receive module which is highly reliable with high repeatable performance in the entire L-band.
Still another object of the present invention is to provide a Transmit/Receive module, which has a very close phase and amplitude level match for all the individual T/R Modules.
Still further object of the present invention is to provide a Transmit/Receive module, which is highly compact and cost effective.
Still another object of the present invention is to provide a Transmit/Receive module which has a self-calibrating and built-in test facility.
Yet another object of the present invention is to provide a Transmit/Receive module which has a distributed beam steering computation facility.
Still another object of the present invention is to provide a Transmit/Receive module, which has a low front-end noise figure.
Still further of the present invention is to provide Transmit/Receive module which has a capability of controlling transmit power output fee realizing low side lobes for transmit radiation pattern.
According to this Invention there is provided a transmit/receive module for a high power active phased array antenna system operating in L-baud based upon a combination of hybrid microwave Integrated circuit (MIC) and monolithic microwave Integrated circuit (MMIC) technology and having power monitoring means (22-25) for on line diagnostic purposes, a transmitter protector means and u receiver protector means, the said transmit/receive module comprising:
signal transmit chain (10) Incorporating power conditioner (33), and signal receive chain (11) incorporating control electronics (37) and bias sequence-modulator (39); wherein, the said signal transmit chain (10) comprises of:
T/P switching means (35), for switching the module to the transmit mode, connected to the transmit amplifier chain (12-20) through shared 6-bit digital phase shifter (36); duplexer means (21) receiving the, amplified signal from the transmit amplifier chain (12-20) sad forming the said transmitter protector means of the said transmit chain (10); a high power switch (23) having a drop in circulator (27) connected to its input end which together with a high power limiter (29) of the said receive, chain (11) form the said receiver protector means of the said receive chain (11) in no power monitoring means (22-25); a Single Pole Single Throw (SPST) switch (26) for on line sampling of transmit power; Tx/Rx Interface PCBs (40,41) for interconnections between the said transmit chain (10) and the said receive chain (11); wherein, the said receive chain (11) receives signal from drop-in circulator (27) and high power switch (28) in receive mode and comprises of: high power limiter (29); RF pre-selection filter (30) connected to the said high power limiter (29); low noise amplifier means (31-33); 6-bit digital attenuator means (34) connected to shared digital phase shifter (36) through T/R switching means (35); all connected through control electronics (37), bias sequencer-modulator (39) and power conditioner means (38).
In accordance with the present invention, the improved Transmit/Receive module for Active Phased Array Antenna elements operating in L-band is realized through hybrid architecture employing both Microwave Integrated Circuit (MIC) as well as Monolithic Microwave Integrated Circuit (MMIC). The use of MIC components in transmit chain of the module helped in generating high power output necessary for long ranging while incorporation of MMIC technology in receive chain of the module helps in miniaturizing the same thus reducing the size of the complete Transmit/Receive module. The proposed Transmit/Receive module can operate in entire L-band providing high peak and average power output with a very high degree of reliability and repeatability. The module is able to provide very close amplitude and phase level matching and tracking for the Transmit/Receive Modules. The Transmit Chain of the module is designed to generate a high peak power output, with a large pulse width and duty over the large RF bandwidth, using Silicon (Si) bipolar transistors operating in efficient class xe2x80x98Cxe2x80x99 mode. Low Noise Amplifier (LNA), Digital Attenuator and Shared Phase Shifter with T/R switches in the Receive Chain of the T/R module, use GaAs (Gallium Arsenide) MMICs for a reliable cost effective solution. Si PIN diodes having high breakdown voltage are used for realizing Receiver Protector Circuitry. The module has an integral on-mounted driver/control circuitry using a microcontroller and miniature hybrid packaging employing SMDs (Surface Mount Devices). The Transmit and Receive Chains are configured using microstrip circuitry on two soft ceramic microwave laminates, which are stacked compactly in a signal T/R module housing. The transmit circuit laminate is screwed on to the integrated liquid cooled cold plate of the module housing, which provides the best cooling efficiency by utilising microchannel cooling underneath each of the power devices of the Transmit Chain. The overall module size is compact and fits in a triangular array grid.
Any further characteristics, advantages and applications of the invention will become evident from the detailed description of the preferred embodiment which has been described and illustrated with the help of following drawings wherein,